Tire design and more specifically tread pattern design plays a critical role in the safe and efficient operation of a vehicle. For example, it is known that the tread pattern assists in the generation of steering forces, as well as driving and braking forces. Also, the tread pattern can improve vehicle performance by reducing road noise, providing superior grip capabilities in both wet and/or dry driving conditions, as well as minimizing rolling resistance to increase the overall fuel economy of the vehicle.
In examining the complex mechanisms involved in proper tread pattern design, several factors play a role in the final design of the tread pattern. These factors include industry standards, government regulations, customer specifications, marketing requirements and the like. On the other hand, the complex mechanisms which are taken into account in the design of the tread pattern include, amongst other mechanisms, stresses generated upon the tire during driving conditions, energy losses due to rolling resistance, sidewall flexing, to a host of other mechanisms. Thus, the design of a tread pattern is not a trivial task and, in fact, is quite complex requiring the need to take into account many different considerations.
In practice, the design of a tire tread pattern also requires the balancing of many contradictory demands. Finding the proper structure that balances these demands for any given tire is thus a great challenge. For this and other reasons, engineers typically focus on a large array of considerations, placing emphasis on certain design criteria over others, depending on the specific application of the tire. However, by focusing on certain design criteria, other criteria such as tire wear or stress components may not have been weighed as heavily during the design stage.
By way of a more specific illustration, one design approach has been to form grooves between ribs with negatively sloped walls to increase gripping capabilities. However, in such an approach, the grooves are more likely to trap and retain stones, which can damage the tire. Another example is in the use of all-season tires, which customarily employ block elements in their tread design. These designs have superior grip performance but tend to have increased noise level, as well as have a tendency toward irregular wear due primarily to their lack of stiffness in the circumferential direction of the tread. Such noise generation and irregular wear are accentuated at acute or sharp angles in the rubber blocks formed by intersections of groove walls.
In any event, tire patterns have common pattern traits. These common pattern traits include, for example, grooves with sharp or acute angles in transitional areas, e.g., between treads, vertical walls forming the grooves or treads, etc. It has been theorized that such designs have large stress components which conjugate at the sharp angles, as well as result in increased road noise and rolling resistance. Of course, engineers are constantly designing tread patterns to increase overall tire efficiency, but these design traits remain pervasive.